Intolerance to the coming-of-age movie will provide only the feeblest defence against the charms of David Robert Mitchell’s debut film, The Myth of the American Sleepover. US cinema produces a great example of the genre every decade or so: American Graffiti and Breaking Away at either end of the 1970s, Dazed and Confused in the 1990s, Raising Victor Vargas ten years ago. Though part of this tradition, Mitchell’s movie is also an unusually delicate specimen. The myth of the title, one character explains, seduces young adults into surrendering the joys of childhood. We swap board games for cider binges, runs the argument, because we believe that adolescence holds something wonderful – as opposed to unmanageable desires, acne like landmines and an urge to write confessional poetry.

Among the film’s dozen or so characters is the bored, bicycle-riding Maggie (Claire Sloma), who makes goo-goo eyes at the pool cleaner; Rob (Marlon Morton), who spies a beautiful girl sniffing shampoo in the supermarket, then extends his search for her into the night; Claudia (Amanda Bauer), who accepts a party invitation from a girl in her athletics club, only to discover they both share a liking for Claudia’s boyfriend; and Scott (Brett Jacobsen), a high-school drop-out who resolves to track down the girl who got away. It takes several scenes to get to know these people but only an instant to know we want to.

Over these romantic imbroglios, set in Michigan on the last weekend of summer, hangs the promise of the sleepover. The girls trundle off to one another’s houses with sleeping bags under their arms; on a leafy corner they meet the boys heading in the other direction for their own pizza-and-horror-movie shindig. There is a glow of wary recognition between the two groups, like once-hostile tribes crossing each other on a wilderness trail. (A rapprochement will come before dawn.) Later, as the camera surveys the various rumpled shapes on living room floors, or the nylon cocoons spread out in a school gym, you feel the mystical spirit of Brigadoon is nearby.

Mitchell’s screenplay is daringly free of wisecracks. His teenagers talk like teenagers rather than Hepburn and Tracy, which is to say falteringly, absurdly, sincerely. (They have no protective layers.) In one delightful “he said/she said” moment, Rob tells his pal about an evening spent with Jen (Mary Wardell): “I think it would have gone further but her mum came home.” Jen, out of earshot, gives her account to a friend: “He sat on my couch eating cheese puffs while I tried to hold his hand.”

The relationships go off at strange tangents. Scott is challenged to guess which twin of an identical pair has the hots for him, while there are several instances of characters being promiscuous with their affections. No one will be surprised that the film discredits its own title, arguing not for adolescence to be regarded as a swizz but for the cherishing of those juvenile summers when we clumsily forge our future selves like fumbling amateur blacksmiths.

What sets the movie apart is its balmy mood. The characters may wend their way toward the Make-Out Maze, a dark, disused factory with lip-locked couples behind every pillar, but there is a decorum to those carnal temptations. “Do you want to sit with me?” asks a girl, popping out of the shadows to accost a male passer-by. “Sorry, I have a girlfriend,” the boy explains, then adds: “I hope you find someone to sit with you.”

Mitchell wrote the script in 2002, which doesn’t quite explain the absence of mobile phones and computers. People here write diaries by hand and there are no pop-culture references to date the movie. Most of the music is obscure; it crackles out of car radios or drifts from distant houses across the lake. Even at its brightest, James Laxton’s cinematography looks bleached out yet the film isn’t exactly nostalgic. You can’t be sure when it’s taking place, other than in a sensual limbo that provides the stage for timeless pleasures – a girl performing an emphatic flapper dance in the moonlight, or a boy creeping along a glowing hallway to glimpse the Palace of Untold Desire - ie, his friend’s older sister in the tub.

Ryan Gilbey is the New Statesman's film critic. He is also the author of It Don't Worry Me (Faber), about 1970s US cinema, and a study of Groundhog Day in the "Modern Classics" series (BFI Publishing). He was named reviewer of the year in the 2007 Press Gazette awards.